Grain weight response to different postflowering source: sink ratios in modern high-yielding argentinean wheats differing in spike fruiting efficiency

Improving wheat (Triticum aestivum L.) yield potential via higher grain number per unit area (GN) may reduce average grain weight and consequently the yield increment would be low. Thirty-nine high-yielding modern cultivars differing in spike fruiting efficiency (FE) (number of grains per gram of no-grain spike) were grown under potential conditions during two temperature-contrasting years to study the level of source limitation during grain filling and rank the main physiological determinants of potential grain weight (PGW) and actual grain weight. The response of grain weight to a 100% higher source ranged from 0 to 25%, depending on cultivar and year. No general relationship was observed between PGW and FE. The stabilized grain water content, which was partially correlated with the endosperm cell number per grain (r2 = 48%, p < 0.05), was the main variable associated to grain weight variation (r2 = 77%, p < 0.00001) in both temperate and warm years. Genetic improvement focused on increasing the sink strength through higher GN is still an alternative to increase yield potential in modern cultivars as no source limitation during grain filling was observed. The improvement of FE could be used to increase GN and yield as no general negative relationship was observed between PGW and FE.Fil: González, Fernanda Gabriela. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aldabe, María L.. Universidad de Buenos Aires. Facultad de Agronomia; ArgentinaFil: Terrile, Ignacio I.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; ArgentinaFil: Rondanini, Deborah Paola. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; Argentin

Integrated Foliar Disease Management to Prevent Yield Loss in Argentinian Wheat Production

Zero tillage often leads to wheat (Triticum aestivum L.) yield losses from diseases caused by necrotrophic foliar pathogens. The aim of this work was to evaluate the combined effect of tillage, N fertilization, fungicides, and resistant cultivars in reducing foliar disease severity to prevent significant yield losses. A 2-yr study including combinations of (i) conventional and zero tillage; (ii) N fertilization rates 0, 80, or 160 kg ha–1 N; (iii) two fungicide treatments (with and without a fungicide (1 L of metconazole, 9%) at growth stages (GS) 32 and 39; and (iv) three wheat cultivars was conducted in the Rolling Pampas region in Argentina. The most common foliar disease in the trial was tan spot [Pyrenophora tritici-repentis (Died.) Drechs.]. Conventional tillage reduced foliar disease severity at GS 23 by 46 and 56% and the area under disease progress curve (AUDPC) by 20 and 14% for each season, respectively compared with zero tillage. The cultivar Buck Bigua had significantly lower AUDPC values than the others. Fungicide and N application reduced disease severity at GS 23 by 35 and 34% respectively, on average over both years. Disease was less severe in zero tillage plots which received a fungicide compared to conventional tillage plots that were not treated with fungicide. In 2002 yields were greater in conventional tillage plots with 160 kg ha–1 N and fungicide application than in all other treatments. In 2003 yields were greatest in zero tillage plots with 160 kg ha–1 N and fungicide. The results of this study indicate that in spite of the increase of necrotrophic diseases, developing no-till systems in wheat monoculture is possible without significant yield losses if effective disease management practices are applied